Torx Size Chart

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Torx Size Chart

Reviewed by MLC Editorial Team | 25 July 2026

Verified by Rachel Mayfield, Supply Chain Analyst - June 2026

A detailed close-up of metallic tool bits arranged on a dark textured surface. — Photo by Pixabay on Pexels

Torx (six-lobe) driver sizes from T6 to T55, with the point-to-point dimension of the lobe in millimetres and typical applications. Torx Size Chart Torx sizes follow ISO 10664, where the T-number is a designation, not a measurement - a T25 has a 4.43 mm point-to-point lobe. The six-lobe drive spreads load over more contact area than a hex or cross head, which is why it resists cam-out and is used widely in automotive and electronics assembly.

Torx size	Point-to-point (mm)	Typical use
T6	1.75	Small electronics, laptop screws
T7	1.99	Phones, cameras
T8	2.31	Laptops, hard drives
T9	2.50	Electronics
T10	2.74	Electronics, small appliances
T15	3.27	Appliances, automotive trim
T20	3.86	Automotive interior, machinery covers
T25	4.43	Automotive, garden machinery
T27	4.99	Automotive engine, brackets
T30	5.52	Automotive suspension, machinery
T40	6.65	Automotive, heavy brackets
T45	7.82	Heavy machinery, structural
T50	8.83	Heavy machinery, suspension
T55	11.22	Construction plant, heavy structural

How to identify a Torx size

If the bit isn't marked, measure the point-to-point width of the star recess with calipers and match it to the table - a 4.43 mm recess is a T25. Going one size too small cams out and rounds the lobes; one size too large won't enter. The most-used sizes in general repair are T20, T25, and T30, which cover most automotive interior and underbonnet fasteners.

Security Torx (Torx TR, also called pin-in Torx) has a pin in the centre of the recess and needs a driver with a matching hole - written as T10H, T20H and so on. A standard Torx bit won't seat in a security Torx screw. External Torx (E-Torx) is the inverse, a star-shaped socket that fits over an external lobed head, sized E4 to E24 and not interchangeable with the internal T-series.

Related standards

ISO 10664 - Hexalobular internal driving feature for bolts and screws
Torx and Torx Plus are trademarks of Acument Intellectual Properties

References

ISO 10664 - Hexalobular internal driving feature

Frequently Asked Questions

What size is a T25 Torx?

A T25 Torx has a point-to-point lobe dimension of 4.43 mm. T25 is one of the most common sizes in automotive and garden machinery work. The T-number is an ISO 10664 designation rather than a direct millimetre measurement.

How do I know what Torx size I need?

Measure the point-to-point width of the star-shaped recess with calipers and match it to the chart - for example 3.86 mm is a T20 and 5.52 mm is a T30. A bit one size too small will cam out and round the lobes, so always use the exact size. T20, T25, and T30 cover most general repair work.

What is security Torx?

Security Torx (Torx TR or pin-in Torx) has a small pin in the centre of the recess to stop a standard Torx bit seating. It needs a driver with a matching centre hole, designated with an H suffix such as T20H. It is used to deter tampering on electronics, public fixtures, and some automotive parts.

References

ISO 10664

Independent UK engineering trade publication. Company profiles cross-referenced with Companies House.